University of Central Florida physicists have found experimental evidence of altermagnetism in Co₁/₄TaSe₂, a layered material baked at over 900 degrees Celsius. The discovery combines characteristics of ferromagnetism and antiferromagnetism without producing unwanted stray magnetic fields, offering a versatile platform for future spintronics and energy-efficient electronic devices.
While everyday life runs on magnetism, researchers have long worked within a binary framework. Ferromagnets create the classic north-and-south-pole attraction seen in refrigerator magnets, but their external magnetic fields can interfere with nearby microchips and computer components. Traditional antiferromagnets cancel out those stray fields because their microscopic magnetic moments point in opposite directions, yet that same internal cancellation makes their states difficult to control and read.
A newly identified magnetic phase bridges those two extremes. Known as altermagnetism, it provides the clean slate of an antiferromagnet alongside the spin-splitting electronic properties traditionally found in ferromagnets. A research team led by the University of Central Florida has now captured direct experimental evidence of this state in Co₁/₄TaSe₂, a layered material containing cobalt, tantalum, and selenium.
Investigators Bake Crystals to Alter Electrons
Creating the material required specialized fabrication techniques. To form usable crystals of Co₁/₄TaSe₂, investigators baked the constituent elements at temperatures exceeding 900 degrees Celsius, roughly 1,700 degrees Fahrenheit, across a two-week period. The resulting compound features layers of tantalum and selenium with magnetic cobalt atoms sprinkled between them, forming a microscopic structure designed to alter electrons as they pass through.
Measurements were conducted well below the material’s magnetic transition temperature of 178 kelvins. At these low temperatures, the cobalt moments form an ordered arrangement where spins align within individual layers but point in opposing directions between neighboring layers. To verify the magnetic state, the research team utilized angle-resolved photoemission spectroscopy, commonly called ARPES, at national synchrotron facilities including the Advanced Light Source at Lawrence Berkeley National Laboratory and the Stanford Synchrotron Radiation Lightsource.
“Our approach was to use higher-resolution methods that were insensitive to the electron’s spin to measure the splitting in the energy levels. Then, we complemented this measurement with spin-resolved ARPES to conclusively tell if this looks like altermagnetism.”
Madhab Neupane, Professor of Physics at the University of Central Florida
Spin Polarization Across Momentum Space
The ARPES scans revealed a characteristic splitting of electronic energy bands that matched theoretical density functional theory calculations. When the team applied spin-resolved ARPES to check whether those separated bands carried distinct spin polarizations, they found that the measured spin polarization shifted from approximately negative 13% to positive 13% across a prominent electronic feature.
Milo Sprague noted that the discovery provides an adaptable platform to study competing electron interactions. Researchers noted that while practical devices remain a longer-term objective, having a tunable material lets physicists explore theoretical debates regarding how spin-polarized electronic states interact with other magnetic phenomena.
“There’s currently a lot of debate in altermagnetic theory about how the spin-polarized electronic states interact with other magnetic phenomena. Now we have a material that we can easily modify to explore these new questions,”
Milo Sprague
Applications in Spintronics and Ultrafast Memory
Future computing architectures aim to move information using electron spin rather than electrical charge alone. Because Co₁/₄TaSe₂ belongs to a family of layered compounds that can be thinned and combined into heterostructures, it offers an unusually flexible medium for investigating these quantum mechanical properties.
The findings, published in Nature Communications, point toward multiple potential technological uses according to the study group. Professor Neupane emphasized the practical advantage of eliminating stray magnetic fields while retaining the ability to control spin currents.
“These materials are distinguished from more conventional antiferromagnets by their ability to generate and detect spin currents without the negative effect of producing stray fields.”
Madhab Neupane, Professor of Physics at the University of Central Florida